Tensile properties of cross-linked woven cellulosic fabrics



July 28, 1970 J; H. SMITH 3,521,995

TENSILE PROPERTIES OF CROSS-LINKED WOVEN CELLULOSIC FABRICS Filed Aug.27, 1965 2 Sheets-Sheet l Tlcl.

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ATTORNEY J. H. SMITH July 28, 1970 TENSILE PROPERTIES OF CROSS-LINKEDWOVEN CELLULOSIC FABRICS Filed Aug. 27, 1965 2 Sheets-Sheet 2,

INVENTOR. ,4f/ 7040 ,6314/ rf/ ATTORNEY United States Patent O 3,521,995TENSILE PROPERTIES OF CROSS-LINKED WOVEN CELLULOSIC FABRICS JosephHarold Smith, Amherst, Mass., assignor to Johnson &'Johnson, acorporation of New Jersey Filed Aug. 27, 1965, Ser. No. 483,043 Int. Cl.D06m 13/14 U.S. Cl. 8-116.3 3 Claims ABSTRACT OF THE DISCLOSURE A methodof improving the tensile strength of crosslinked cellulose fabrics bytreating the fabric with a swelling agent and applying tension in thefilling direction of the fabric and removing the swelling agent from thefabric while under tension. The fabric is then dried and treated with across-linking agent to cross-link the cellulose.

This invention relates to improved methods for crosslinking wovencellulosic fabrics, and more particularly to an improved method forcross-linking cellulosic fabrics which have initially been treated witha swelling agent for cellulose so that the resultant fabric retains agreater percentage of its original tensile strength and tear strength.

In recent years wash and wear goods, especially resintreated cellulosicfabrics, have gained in importance in the apparel industry. Generallythese fabrics are made by treating the base cellulosic fabric withthermosetting resins or other types of cross-linking reactants tocross-link the hydroxyl groups of the cellulose and give the fabricdimensional stability, crease-resistance, etc. The greatest probleminvolved in this type of treatment is the losses which occur in thetensile properties of the fabric, especially the tensile strength andespecially in the filling direction of the fabric. This is also true offabrics which have first been treated with a swelling agent to improvetheir luster, sheen and dyeability.

I have discovered a method for making cross-linked woven cellulosicfabrics which have been treated with a swelling agent which retain agreater percentage of their original tensile strength, even up to 80 to90 percent of their original tensile strength and which have improvedtear strengths over standard cross-linked fabrics.

lIn accordance with my improved method, fabrics may be treated by mymethod and stored and later treated with a cross-linking agent and stillhave improved tensile properties.

In accordance with the present invention, woven cellulosic fabrics aretreated with an agent to swell the cellulose. The fabrics are placedunder tension in the filling direction and while under tension, theswelling agent is removed usually by washing the fabric with water. Theswollen cellulosic fabric is dried. The fabric is further treated with across-linking agent by impregnating it with such a resin, drying thefabric and curing it to react the cross-linking agent with thecellulose. The resultant fabric retains a greater portion of itsoriginal tensile strength than does a similar fabric treated in asimilar manner but with no tension applied in the filling-wisedirection. In the preferred embodiment of the present invention, wovencotton fabrics are treated with caustic solutions of the mercerizingtype to mercerize the fabric. Tension of at least .03 pound per threadis applied in the filling-wise direction and preferably from about 0.05to 0.2 pound per thread tension is applied, and the fabric washed withwater to remove the caustic. The washed fabric is dried and is eitherimmediately or after a period of time impregnated with any of the knownthermosetting resins or similar resins for wash and wear treatment. Theimpregnated ice fabric is dried and cured to react the resin with thecellulose.

The invention will be more fully understood from the description whichfollows taken in conjunction with the accompanying drawings.

In the drawings:

FIG. l is a simplified diagrammatic process flow sheet of the method ofthe present invention;

FIG. 2 is a schematic side view of apparatus for carrying the method ofthe present invention into operation; and

FIG. 3 is a diagrammatic view in plan of apparatus for carrying out themethod of the present invention.

Referring to FIG. l of the drawings, the first step in the method of thepresent invention is to treat standard woven cellulosic fabrics madefrom either cotton yarns, rayon yarns, mixed yarns, i.e., blends ofcellulosic fibers and other fibers, etc., with a swelling agent for thecellulose (Box 10). Suitable swelling agents are amines, sodiumhydroxide, potassium hydroxide, zinc chloride, quarternary ammoniumbases, etc. It is preferred that the fabric be treated so as tomercerize the fabric, that is, by treating the fabric with from about 2Oto 30 percent caustic for a period of time from about 30 seconds to 8minutes at a temperature from about 65 F. to 105 F. The swollen fabricis then washed, preferably with water, to remove the swelling agent (BOX11). If desired, this may take a number of steps and in some instancesdilute acid may be used to neutralize the caustic or the swelling agentused. It it essential to the present invention that when the swellingagent is being removed that tension be applied to the fabric in thefilling direction. This tension may vary from about .03 pound per threadto a tension just below the rupture point of the threads. It ispreferred that this tension be applied for a sustained period of time ofat least 10 seconds. The fabric washed under tension is dried to removethe water (BOX 12). The fabric may be dried at various temperatures, forvarious times of from about F. to 250 F. for times of from about 1minute to 4 minutes.

The fabric may be stored in this condition for considerable lengths oftime or it may be used immediately dependent on what is desired. Themercerized or swollen and dried fabricis impregnated with an agent whichwill cross-link the cellulose (Box 13). Suitable cross-linking agents,either acid or base catalyzed, are the thermosetting resins, such as theurea formaldehydes, melamine formaldehydes, sulfones, etc. Generally asolution, preferably an aqueous solution, of the cross-linking agent ispadded on the fabric so the fabric picks up from about l percent toabout 10 percent by weight of the fabric. A catalyst may also be appliedto aid in the cross-linking reaction. The impregnated fabric is dried toremove the water at temperatures of from about 100 F. to 250 F. forperiods of time from l minute to 5 minutes (Box 14). The dried fabricwith the cross-linking agent thereon is then heated at an elevatedtemperature of from about 325 F. to 400 F. to react the cross-linkingagent with the cellulose and cross-link the cellulose (Box 15).

Referring to FIGS. 2 and 3 of the drawings, there is shown the preferredmethod for carrying the present invention into practice. A roll 20 ofwoven cellulosic fabric F is passed through a bath 21 of sodiumhydroxide 22. The fabric is maintained in this bath for a period of timeby passing it over rollers 23 so that it has an immersion time of fromabout 30 seconds to about 8 minutes. Upon being removed from this bath,the fabric is placed on a tenter frame 24. The tenter frame comprises apair of diverging endless chains which have clips 25 to grip the fabric.The fabric upon leaving the bath is clipped at each edge and as thesechains diverge the fabric is placed under tension in the filling-Wisedirection. While under this filling-wise tension, the fabric is Washedby spraying it with water through the nozzles 26. This washing removesthe caustic. The fabric is then dried by passing it under the heatingoven 27 or over a set of dry cans if desired. The dried fabric is thenpassed through a padder comprising a bath 28 containing a solution ofthe cross-linking reagent 29. In the bath are a pair of rolls 30, and asthe fabric passes through the nip of these rolls it is impregnated withthe cross-linking agent. Upon leaving this impregnating bath, the fabricis placed on a permeable conveyor 3].. It is passed under radiantheaters 32 to remove the water and dry the fabric, and passed through anoven 33 to cure the fabric, that is react the cross-linking agent withthe cellulose. The resultant fabric 34 is wound up in accordance withstandard procedures.

The invention will be further illustrated in greater detail by thefollowing specific examples. It is to be understood, however, thatalthough these examples may describe in particular detail some of themore specific features of the invention, they are given primarily forpurposes of illustration and the invention in its broader aspects is notto be considered as limited thereto.

EXAMPLE I An all cotton fabric having 85 warp yarns per inch and 80 fillyarns per inch is slack mercerized by passing it through a solution of22 percent caustic at a temperature of 75 F. for a period of time of 4minutes. The fabric is washed with water and dried at a temperature of250 F. This fabric is treated with an aqueous solution of 17 percenturea formaldehyde resin sold by American Cyanamid Co. under the tradename Aerotex Resin 52. and 1.7 percent of an amine hydrochloridecatalyst sold by the Crown Chemical Co. under the tradename Catalyst CC.The fabric is dried at 250 F. for 2 minutes and cured to react thecross-linking agent with the cellulose at 325 F. for a period of 2minutes. Absolutely no tension is applied in the filling direction ofthe fabric during this treatment. The resultant fabric has a tensilestrength in the filling direction of .180 pound per thread or 36 percentof its original filling tensile strength. The tear strength of thefabric in the filling direction is .71 pound.

EXAMPLE II The fabric as described in Example I is treated as describedin Example I with the exception that tension is applied in the fillingdirection of the fabric in the amount of .05 pound per filling thread,While the caustic is being washed from the fabric. The resultant fabrichas a tensile strength in the filling direction of .274 pound per threador 55 percent of its original tensile. It has a tear strength in thefilling direction of .92 pound.

EXAMPLE III The fabric as described in Example I is treated as describedin Example I with the exception that 0.10 pound per thread of tension isapplied in the filling direction of the fabric, While the caustic isbeing washed from the fabric. The resultant fabric has a tensilestrength in the filling direction of .300 which. is 60 percent of itsoriginal tensile, and a tear strength in the filling direction of .85pound.

EXAMPLE IV An all cotton print cloth, not mercerized, which is 381/2inches wide and containing 64 warp yarns per inch and 56 fill yarns perinch is padded at a 38-inch width with an aqueous solution of percenturea-formaldehyde resin sold by American Cyanamid Co. under the tradename Aerotex Resin 52 and 1.5 percent of an ammonium hydrochloridecatalyst sold by Crown Chemical Co. under the trade name Catalyst CC.The fabric picks up 5 percent by weight of resin. The fabric is dried atthe 38- inch width at 250 F. and cured to cross-link the cotton with theresin at 325 F. The resultant fabric has a tensile strength in thefilling direction of .261 pound per thread or 61 percent of its originaltensile strength and a tear strength in the filling direction of 1.13pounds.

EXAMPLE V A similar piece of fabric as that described in Example IV istreated as described in Example IV except that prior to resin threatmentit is mercerized in 22 percent sodium hydroxide for 4 minutes at 75 F.,washed with water while tension of 0.091 pound per thread is applied inthe filling direction and dried at 250 F. for 2 minutes. The resultantfabric after resin treatment as described in Example IV has a tensilestrength in the filling direction of .284 pound per thread or 99 percentof its original tensile strength and a tear strength in the fillingdirection of 2.26 pounds.

Although several specific examples of the inventive concept have beendescribed, the same should not be construed as limited thereby nor tothe specific features mentioned therein but to include various otherequivalent features set forth in the claims appended hereto. It isunderstood that any suitable changes, modifications and variations maybe made without departing from the spirit and scope of the invention.

What is claimed is:

1. A method of improving the tensile strength of a cross-linked, wovencotton fabric comprising: treating a woven cotton lfabric with asolution of from about 20 percent to about 30 percent sodium hydroxideat a temperature of from about 65 F. to 105 F. for a period of time offrom about 1 minute to 4 minutes to cause the cotton to swell, applyingat least .03 pound per thread of tension in the filling direction tosaid swollen fabric, while said fabric is under tension washing thefabric with water to remove the sodium hydroxide, heating the fabric toa temperature of 'from about 100 F. to about 250 F. to remove the water,impregnating the dried fabric with from about l percent to about 10percent by weight of the fabric of a cross-linking agent for cellulose,selected from the class consisting of urea-formaldehyde resins,melamine-formaldehyde resins, and sulfones, heating the fabric to atemperature of from about 100 F. to about 250 F. and treating the fabricat a temperature of from about 325 F. to about 400 F. to react saidcross-linking agent with the cotton.

2. A method of improving the tensile strength of a cross-linked, wovencotton fabric comprising: treating a woven cotton fabric with a solutionof from about 20 percent to about 30 percent sodium hydroxide at atemperature of from about 65 F. to 105 F. for a period of time of fromabout 1 minute to 4 minutes to cause the cotton to swell, applying atleast .03 pound per thread of tension in the filling direction to saidswollen fabric, while said fabric is under tension washing the fabricwith water to remove the sodium hydroxide, heating the fabric to atemperature of from about 100 F. to about 250 F to remove the Water,impregnating the dried fabric with from about 1 percent to about 10percent by weight of the fabric of a melamine-formaldehyde resin,heating the fabric to a temperature of from about 100 F. to about 250 F.and treatin-g the fabric at a temperature of from about 325 F. to about400 F. to react said melamineformaldehyde resin with the cotton.

3. A method of improving the tensile strength of a cross-linked, wovencotton fabric comprising: treating a Woven cotton fabric with a solutionof from about 20 percent to about 30 percent sodium hydroxide at atemperature of from about 65 F. to 105 F. for a period of time of fromabout 1 minute to 4 minutes to cause the cotton to swell, applying atleast .03 pound per thread of tension in the filling direction to saidswollen fabric, while said fabric is under tension washing the fabricwith Water to remove the sodium hydroxide, heating the fabric to atemperature of from about 100 F. to about 250 F. to remove the water,impregnating the dried fabric with from about 1 percent to about 10percent by weight of the fabric of a urea-formaldehyde resin, heatingthe fabric to a temperature of from about 100 F. to about 250 F. andtreating the fabric at a temperature of from about 325 F. to about 400F. to react the urea-formaldehyde resin with cotton.

References Cited UNITED STATES PATENTS 3,145,132 8/1964 Seltzer 8-120 XR6 OTHER REFERENCES Tripp et al.: Some Relationships BetweenSupermolecular Structure, Etc., Textile Research Journal, pp. 404-416.

S. P. Hersh et al.: Eiect of Tension on the Properties of Resin-TreatedCotton Fabrics, Textile Research Journal (1962, April) pp. 271-284.

JOHN DAVID WELSH, Primary Examiner U.S. Cl. X.R.

